Measure your daily noise dose

The science of hearing loss uses the concept
of “noise dose” to establish an equivalent
relationship between different combinations
of noise levels and durations of exposure. As
either the noise level or the duration of exposure
goes up, so does the dose.

Damage risk criteria are developed using mathematical
modeling based on studies that show the
dose-response relationships. These studies
show that, in general, the ear sustains damage
after about an eight-hour exposure to noise of
80 decibels.

In hearing conservation, nearly every occupational
noise exposure standard around the
world expresses the balance of noise and duration
through a Permissible Exposure Limit
(PEL) or criterion level for noise. Such limits
are set based on an analysis of specific health
risks and the cost/benefit of limiting exposure
to that hazard. For noise, OSHA and most
other U.S. standards set the PEL at 90 dB of
noise exposure over an eight-hour time period.
Worldwide, the majority of PELs for noise are
set at 85 dB over eight hours.

In fact, NIOSH estimates that about 92
percent of workers should be safe from noise-induced
hearing loss over their lifetime of
exposures if they are protected to an average
exposure equivalent to less than 85 dB over an
8-hour shift [NIOSH Criteria Document (1998)
http://www.cdc.gov/niosh/docs/98-126/chap3.
html].

Hearing protection: steps to success
There are several actions we can take to
promote hearing safety by preventing an “overdose”
of noise:

Engineering controls (limit the noise
level at its source)

Administrative controls (limit individual
exposure time)

Personal protective equipment (hearing
protectors)

We often teach that if you need to raise your
voice in order to speak to someone an arm’s-length
away, the noise is likely at a hazardous
level. But this “arm’s-length rule” does not
tell how much of a hazard is present or if the
worker is protected with hearing protection.

Recent advances in intelligent hearing pro-
tection technology
enhance our
ability to protect
people from hazardous
noise exposures and
measure one’s daily dose.
Earplug fit-testing systems
can measure how well hearing
protection works for each individual,
and in-ear-dosimetry technology
measures exactly how much
noise reaches the ear, even with hearing
protection.

These new tools enable workers to use
hearing protectors better and to improve selfefficacy.
Self-efficacy is defined as a person’s
belief about his or her ability and capacity to
accomplish a task or the power or capacity to produce
a desired effect: effectiveness. Your sense of
self-efficacy plays a major role in how you approach
goals, tasks and challenges, including the use of personal
protective equipment (PPE). If you know how
to use PPE and trust it to protect you, you are more
likely to use it appropriately.

A key to worker empowerment is quantitative
feedback, be it on the fit of earplugs or on the overall
noise dose experienced during the course of the
workday. This feedback is critical to worker empowerment
â€” and to the success of any hearing conservation
program.

Quantitative feedback
With earplugs, providing quantitative feedback
helps the individual recognize a poor fit compared
to a good fit. In a recent trial, volunteer construction
workers completed two to four quick fit testings
of their earplugs. When the volunteers were ready
(some after only one or two practice tests, others
after three), they performed their final quick fit-test
and were asked to report the level of attenuation
(noise reduction) they thought they were getting by
5 dB increments.

Over half predicted their attenuation within
the correct 5 dB increment.

Only 11 percent were “off” by more than one
5 dB category in their self-assessment of the amount
of attenuation for a given ear.

Half of those erroneous self-assessments
underestimated the protection level, and half overestimated
the protection level.

Three of the four individuals who had erroneous
self-assessments were, in fact, consistently
achieving adequate levels of attenuation for their
noise environment.

Earplug fit-testing can identify those individuals
who need more hearing safety training either to
achieve appropriate protection or to recognize the
level of protection they are achieving. Once workers
have an appropriate level of self-efficacy, they are
empowered to safeguard themselves with the use of
hearing protectors â€” not only on the job but during
recreational or off-the-job exposures as well.

Real-time feedback
In-ear dosimetry provides an even greater level
of personal feedback. The in-ear dosimeter is a
continuous monitor of a worker’s noise dose with
and without protection during the work shift. It also
provides real-time alerts when the worker is being
over-exposed and when the worker’s overall dose
has exceeded safe limits. These warnings teach â€”
in realtime
â€”
which tasks
or areas are
associated with
hazardous noise
and whether the hearing
protection is, in fact,
effective.

In addition to these realtime
warnings, the in-ear
dosimeter’s software allows
for notification of a supervisor or
occupational safety professional when
docked and downloaded at the end of
a shift. Occupational health and safety
professionals are now empowered with a
leading indicator and can then take immediate
steps to employ better hearing protection for
each worker going forward.

Research has shown that self-efficacy is an
important factor in the use of hearing protection.
Knowing the level of noise reduction provided by
hearing protection and the individual dose of noise
and being able to control that dose can improve
self-efficacy, empowering workers to avoid overexposure
to hazardous noise and noise-induced hearing
loss.

Dr. Theresa Y. Schulz is the hearing conservation manager for Honeywell Safety Products, manufacturer of Howard Leight® hearing protection products (www.howardleight.com, www.hearforever.org). She is a past president and has been an active member of the National Hearing Conservation Association [NHCA] for 30 years. Dr. Schulz served in the U.S. Air Force for over 20 years as an audiologist.

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